Equilibrium constant is an important property of a chemical reaction. It indicates the direction of — Analytical Chemistry Chemistry Question
Determination of an Equilibrium Constant
Equilibrium constant is an important property of a chemical reaction. It indicates the direction of a reaction. The concentration of each reaction species can be calculated from the equilibrium constant. For a reaction of the type
a A + b B = c C + d D,
the equilibrium constant, Keq, is given by the expression:
Keq = [C]^c [D]^d / ([A]^a [B]^b)
From the equation, Keq can be easily computed if the concentrations of all species at equilibrium are known. Once the Keq is determined, concentrations at equilibrium can be calculated from any given starting condition.
The aim of this experiment is to deduce the Keq for the reaction of Fe(NO3)3 with KSCN. You are provided with 20 cm3 of a starter of each of the reactant: Fe(NO3)3 and KSCN with a concentration of 0.1 mol dm-3. Three test tubes containing the product from the reaction are also provided. Each of these contains the product with a known concentration (in mol dm-3) of: 3.214×10-3, 1.360×10-3, 1.375×10-4 for tubes 1, 2, and 3; respectively. These standard solutions are used as a colorimetric reference.
You have to design an experiment to determine the Keq for the reaction of Fe(NO3)3 with KSCN using the given reagents. Your data should be listed in a table as shown below:
[VISUAL]
Carefully design your experiment before you start. More reagents can be obtained from the TAs upon request. However, 5 points will be deducted for each additional reagent. Marks for this experiment will be primarily awarded on the basis of the accuracy of the result.
Besides the reactants, the following equipment has also been provided on your bench:
Sheets of paper 3
Kimwipe, 1 box
Labels
Test tubes 20
Test tube rack 1
Safety bulb 1
Rubber bulbs 4
Pipettes 4
Glass rods 2
Test tube brushes 2 (thin and thick, one each)
Wash bottle 1
Ruler (15 cm) 1
Beakers, 100 cm3 2, 250 cm3 2, 500 cm3 2
1. Graduated cylinders, 10 cm3 1, 25 cm3 1
2. Volumetric flasks, 25 cm3 , 2
3. Erlenmeyer flask, 100 cm3 4
4. Burets, 5 cm3 2, 1 cm3 2
Write a balanced equation for the reaction.
What is the expression for the equilibrium constant of this reaction?
Keq =
What is the calculated value of Keq from your data sheet?